If a woman goes to a public beach area and is fully dressed, can she swim in the water? How much of a distance from men is necessary for a woman to have in order to be able to swim in the public water?
Yes, provided her robe will not rise and there is no chance of men seeing the parts of the body which need to be covered.
However, if there are men there dressed inappropriately or even women who are dressed in a Priztusdik manner it is not appropriate to go there.
ראה גיטין צ, ב. מל״ח ט, כז. משנ״ב שלט בבה״ל ד״ה להקל. אג״ק יח ע׳ סב. בא״מ ד, קמז. יחו״ד ה, סג.
וראה הנסמן בגן נעול יג, מ-מא-מב.